Download METAMORPHIC ROCKS

FORMATION OF METAMORPHIC ROCKS
 Metamorphic rocks form when existing rocks undergo metamorphism (to
change).
 Metamorphic rocks began as either an igneous, sedimentary or another
metamorphic rock...we call the beginning (1st) rock the parent rock.
 The parent rock is under tons and tons of pressure, which causes heat to
build up, causing the parent rock to SOFTEN or RECRYSTALLIZE and
change or “morph” into a metamorphic rock
Parent Rock
Granite (Ign)
Sandstone(Sed)
Shale(Sed)
Limestone(Sed)
Shale (Sed)
morphs into
morphs into
morphs into
morphs into
morphs into
morphs into
Metamorphic Rock
Gneiss
Quartzite
Slate
Marble
Schist
Types of Metamorphism:
1. Contact Metamorphism-When magma forces its way into rock, and elevates
temperatures enough to alter the rock. Minor changes result.
2. Regional Metamorphism-Occurs over large areas of the Earth when tectonic
plates collide and mountains are built.
The picture at the left
SEDIMENTARY ROCK
Is this contact or regional
metamorphism?
IGNEOUS ROCK
Metamorphic rock (marked altered)
formed when the sedimentary rock
surrounding the magma was
softened (NOT MELTED) by the heat
from the magma.
The melted rock becomes an
igneous rock
Agents of metamorphism are
1. heat---provides energy to drive the chemical
reactions
2. pressure---makes rocks compact and dense,
makes folds in rocks
3. fluids---solutions that make it easier for
minerals to move and recrystallize
METAMORPHIC ROCKS are classified based on texture
and are either FOLIATED OR NONFOLIATED
1. FOLIATED
• When the parent rock softens the mineral grains are
flatten by the heat and pressure
• This causes the metamorphic rock to show a striped or
banded look in some rocks
• Examples of foliated metamorphic rocks are gneiss, schist and slate
GNEISS
Which sample shows foliation? _____
Which sample is showing fine-grained igneous rock? _____
Which sample is showing a sedimentary rock? _____
2. NONFOLIATED
 Mineral grains grow and rearrange, but do not form bands or stripes
 Examples of nonfoliated metamorphic rocks include quartzite and marble
Quartzite
Quartzite
magnified
No bands
AMAZING EARTH SCIENCE FACTS

Metamorphic rocks are formed by _____________________________________.

Metamorphic rocks include:
1. ________________________ (banded)
 Examples are slate, schist and gneiss
2. ________________________ (no stripes)
 Examples include marble and quartzite

Parent Rock
Limestone
Sandstone
Shale
morphs
morphs
morphs
Metamorphic Rock
into ___________________
into ___________________
into ______________ and then into ____________
Metamorphic Key Words Include:
heat
pressure
recrystalization
banded
striped
nonfoliated
foliated